The Boston bombing suspect was crammed on the floor of a boat as law enforcement closed in during Friday's massive manhunt, according to newly released aerial video.

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A helicopter, using thermal imaging, caught the action as the arm of an armored tank peeled back tarp that covered the 24-foot boat — which was parked behind a residential home in Watertown, Mass.

Dzhokhar Tsarnaev’s feet can be seen at the center of this image captured by an infrared device. (Massachusetts State Police)

Then, small explosives — believed to be flash-bang grenades — were tossed into the front of the boat in an attempt to stun Tsarnaev. Such devices are non-lethal.

Earlier still images released by Massachusetts State Police were of those same dramatic moments before Tsarnaev was captured. The new video doesn't include sound.

"We have what's called a FLIR — a forward-looking infrared device — on that helicopter. It picked up the heat signature of the individual," said Col. Timothy Alben of the Massachusetts State Police.

When the boat's owner lifted up the tarp covering his boat, he saw a pool of blood and what he thought looked like a body, according to reports. (Massachusetts State Police)

Police had the helicopter fly over the man's house after he reported that a bloodied person was holed up in his boat, which was just outside the search perimeter police set up earlier in the day.

Although obstructions — such as the boat tarp — can prevent light from passing through, heat waves can still be detectable, said NBC News.

Authorities saw what is called an infrared signature — the way an object or person appears beneath thermal sensors. Infrared signatures can help monitor volcanoes or detect diseases, but it also helped police monitor Tsarnaev's body for more than an hour.